itch.io

I haven't played it, but if its about the games having the same model resource, than I can say that it happens often. Since many AVNs on this website is built on the same "engine", you can often find the different games looking at felling similar in some scenes.

you can check the discord server

For the sake of you playing in the future I won't go into the details. 

little bit of spoilers, since everything is explained later in the game.

Yes, Rule B and Gab are the same person (that much is to be expected), and he's also the MC's older brother. Nael IS the strongest Dark One, and will not be part of the harem. Claire in't evil, she is just very cunning and tries to protect Clara. Your questions about the MC can't be answered yet because the game hasn't come that far yet. 

Are you asking these questions to get answers or is it purely justing rhetorical? Because I don't think you'd like the answers to those question based on the last part of what you said.